21. CHECKS AND ADJUSTMENTS
146
If the survey point is on the solid line (dotted line):
Loosen the right (left) adjusting screw slightly and,
tighten the left (right) adjusting screw by the same
amount to move the survey point to a point in the
center of the optical plummet.
6. Check to make sure that the survey point remains
centered on the reticle even if the upper part of
the instrument is rotated.
If necessary, perform the adjustment again.
7. Replace the optical plummet reticle cover.
The additive distance constant K of the instrument is adjusted to 0 before delivery. Although it almost
never deviates, use a baseline with a known distance precision to check that the additive distance
constant K is close to 0 several times a year and whenever the values measured by the instrument
begin to deviate by a consistent amount. Perform these checks as follows.
G
• Errors in setting up the instrument and reflective prism or in sighting the target will influence the
additive distance constant. Be extremely careful to prevent such errors when performing these
procedures.
• Set up so that the instrument height and the target height are identical. If a flat place is not available,
use an automatic level to make sure the heights are identical.
PROCEDURE Check
1. Find an area of flat ground where two points
100m apart can be selected.
Set up the Instrument at point A and the reflective
prism at point B. Establish a point C half way
between points A and B.
2. Precisely measure the horizontal distance
between point A and point B 10 times and
calculate the average value.
21.7
Additive Distance Constant
4
(3)
3
(4)
